Tribological properties of MoS2 coating for ultra-long wear-life and low coefficient of friction combined with additive g-C3N4 in air

Abstract

Abstract The solid lubricant MoS 2 demonstrates excellent lubricating properties, but it spontaneously oxidizes and absorbs moisture in air, and thus results in poor wear resistance and short wear-life. In this study, the additive g-C 3 N 4 (CN) was successfully combined with MoS 2 via hydrothermal synthesis as a solid lubricant for the first time. Meanwhile, a low friction coefficient (COF, μ = 0.031) and ultra-long wear-life of CN/MoS 2 compared to pure MoS 2 in air were demonstrated. The functional groups and good crystallinity of the lubricant material were characterized via Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The formed valence states in CN/MoS 2 were analyzed via X-ray photoelectron spectroscopy (XPS). The characterized results of the scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) show the morphology and interior crystal phase structure of CN/MoS 2 . From the cross-section analysis, the presence of iron oxide nanoparticles lubricating film is synergistic with CN/MoS 2 film during the friction process, resulting in its ultra-long wear-life. In particular, the friction mechanism of interlayer sliding friction combined with energy storage friction was analyzed and proposed.